Urine potassium (K), Quantitative 24 urine or Random sample

Sample

1. Collect 24 hours of urine.
2. Procedure to collect 24-hour urine: Discard the first sample and note the time.
3. Collect the rest of the urine for 24 hours and urinate the last sample into the container.
4. Refrigerate the urine during collection.

Indications

1. This study is done in renal and adrenal disorders.
2. This is done for water and acid-base balance.
3. This is done in the support of hypercalcemia.

Precautions

1. Potassium in the diet will affect the urinary potassium level.
2. Drugs which increased the potassium level are diuretics, salicylates, and glucocorticoids.
3. Licorice increases the potassium excretion in the urine.

Pathophysiology

1. Potassium is the major cation within the cells (Intracellular).
2. Potassium concentration depends upon:
   1. Aldosterone.
   2. Glucocorticoids.

3. Kidneys are important for the regulation of the K level.
   1. Kidneys can not reabsorb the potassium.
   2. Intake of potassium is balanced by the kidneys by excretion of potassium in the urine.
   3. Proximal tubules reabsorb all the K.
   4. Aldosterone additional K excreted into the urine in exchange for Na.
   5. The distal nephron is the main determinant of urinary K excretion.

4. Even if an excess of K taken, still this is excreted in the urine except in patients with renal failure where K level may enter into the toxic level. This is an active process that depends upon ATPase activity.

5. This is the amount of potassium excreted in the urine.
6. In the case of Alkalosis, there is increased secretion of Potassium in the urine.

7. In the case of acidosis, there is decreased secretion of potassium in the urine.

8. Urine K+ >30 meq/day is inappropriate in hypokalemic patients and strongly suggest a hyperaldosteronism state.
   1. Spot urine test K⁺ > Na⁺ is also suggesative.
9. Urine K⁺ <30 meq/day reflects renal  K⁺ retention as seen in the diuretic use or gastrointestinal loss.

NORMAL

Source 1

Age	meq/day
6 to 10 years
Male	17 to 54
Female	8 to 37
10 to 14 years
Male	22 to 57
Female	18 to 58
Adult	25 to 125

• Values vary with diet.

Source 2

• 25 to 100 meq / L / day (25 to 100 mmol/day).
  • Values vary with diet.

Increased urinary Potassium level is seen in:

1. Diuretic therapy.
2. Cortisone therapy.
3. Drugs like penicillin and carbenicillin
4. Thiazides.
5. Chronic renal failure.
6. Starvation.
7. Hyperaldosteronism.
8. Renal tubular acidosis.
9. Cushing’s syndrome.
10. Alkalosis.
11. Excessive intake of licorice.

Decreased urinary Potassium level is seen in:

1. Diazoxide.
2. Amiloride.
3. I/V glucose infusion.
4. Dehydration.
5. Malnutrition.
6. Diarrhea.
7. Vomiting.
8. Malabsorption.
9. Addison disease.
10. Acute renal failure where urinary K will be low but the patient will have hyperkalemia.

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